Wind turbines usually comprise a tall and slender tower. At the top of the tower, the nacelle, which is housing the generator and the rotor, is located. Additionally, the hub with the rotor blades is located at the top of the tower. Thus, the center of mass of the wind turbine is positioned relatively high above the ground. Consequently, the wind turbine is prone to movements, for instance due to wind loads or earthquakes. Wind loads comprise continuous wind flow as well as extreme wind gusts. These movements of the wind turbine are normally undesired as they add structural damages to the wind turbine.
Thus, the development of a system to damp these undesired movement of the wind turbine is an active field of research. A commonly used design of a damper for a wind turbine tower is a flat circular disc which, for instance, has a hole in the middle. The flat circular disc may have a liquid inside which damps linear motion of the wind turbine tower by providing the liquid sloshing from side to side. The damping of a circular or elliptical movement of the wind turbine tower is provided by a liquid wave moving along the rim of the damper.
In the state of the art, the flat circular disc is manufactured in one piece and is usually made of plastic.
Such a liquid damper, however, has several disadvantages. First, it cannot be disassembled easily. As a consequence, transport of the damper from the production site to the installation site as well as the installation of the damper itself is complex and costly. Furthermore, a replacement or a repair of the damper is difficult, if not impossible at all.
Another disadvantage of a damper which is manufactured in one single piece is that redesigning the damper is complex and costly as it has to be carried out for each new wind turbine type. In other words, an adaption of the design of the damper is costly as no standard elements can be used. As an example, new manufacturing moulds have to be created for each new design of a damper.
These disadvantages and problems have been solved up to now by, for instance, using several small dampers. Small dampers are easier to transport and to install in the wind turbine. The problem of a difficult replacement and repair of a damper according to the state of the art has been solved up to now by accepting certain leakage of dampers, particularly of large dampers which can hardly be replaced.
However, these solutions are not satisfying as they actually do not overcome the existing problems and disadvantages.
Thus, there is a need for a damper that is easy to integrate in a wind turbine, and, if once incorporated to the wind turbine, is easy to disassemble again, e.g. for repair.